The invention concerns a filter element, in particular for use as an air filter in an internal combustion engine, as well as a filter system for installation of such a filter element.
DE 297 80 439 U1 discloses air filter configurations in which the filter element and the housing are constructed such that a “pre-cleaning” process takes place that already removes coarse dirt from the air before the air is coming into contact with the filter element. For example, housings are constructed with respect to an incoming air stream such that the air is first guided in a circular flow or a screw pattern about the filter element (or so as to circumscribe it) so that coarse dirt particles or suspended particles are already separated from the air due to a cyclone effect.
In conventional systems, the incoming air causes considerable turbulence at the inlet opening into the system. Such turbulence can stress or weaken at this location the folds of the paper medium employed as a filter medium and this leads to weakening or sometimes even failure of the paper medium at this location. In some systems, the housing provides an inner structure in order to prevent this. Moreover, in the vicinity of the air inlet into the circular flow system, the air stream can be guided to a certain degree against the folded paper medium, in particular when the housing at this location has no protective structure. This can cause premature clogging of the filter medium at this location with coarse suspended particles. Moreover, the suspended particles can damage the medium when the particles are guided against the medium at this location.
According to DE 297 80 439 U1, the filter element therefore comprises a lining that provides a mechanical protection of the filter element, an area comprised of filter medium, and a shielding arrangement. The lining has open areas for passage of air. The shielding arrangement is arranged at a perforated or open part of the lining at a downstream surface in the direction of the air flow in such a position that it shields a connected part of the lining and a part of the filter medium from direct passage of air. The lining can be expanded metal lath and the shielding arrangement can be a polymer film or polymer foil.
The object of the invention is to provide a filter element with an incoming flow protector against direct incoming flow of a filter medium that can be produced efficiently and inexpensively.
A further object of the invention is to provide a filter system for receiving such an exchangeable filter element with an incoming flow protector that can be produced efficiently and inexpensively.